One is aesthetic, and concerns the opportunity of removing the substances laid upon it during the previous restorations; the other is technical, and concerns the methods of restoration and preservation.

To restore a supposed original look to the painting, today's restoration wants to remove all the superimpositions of colour and varnish.

But the work done till now demonstrates that the result will be that of reducing Leonardo's masterpiece to the first film of colour, which is constituted by mineral pigments.

Now it is necessary to verify if this first coloured film is entirely by Leonardo, or if, on the contrary, it was made also with the help of Leonardo's pupils.

Everybody knows that, at that time, in the first stage of such works - that is the drawing up with "dull" colours (mineral) - tke pupil's help was customary.

The first execution served as priming coat, or "campo", for the final elaboration, which only the Master carried out by means of "bright" colours (organic), orchestrating his personal chromatism.

These "bright" colours, also called "lacquers" are transparent and they need a light priming coat ("campo") to reveal their beauty and typical vividness and transparency.

Before colouring with these lacquers, it is necessary to fix the mineral colours of the priming coat with a fluid varnish.

Obviously, then, the lacquers must be fixed with a final varnish.

If, in restoring the missing parts of a picture, a restorer uses new organic colours and, with these, he overlays the old ones and then, be varnishes, all glazings may become a confused mixture because of their physical impalpability.

Then one must remember that the first restoration of the "Cena" was made by Leonardo himself. Now, to tell the true from the false, the only means is to compare artistic values with well preserved works of the Artist, with works, above all, that were never restored.

For example: the "Gioconda", which is considered a well preserved work, possesses a strong power in its general tonality and a strong evidence in its form due to the consistence of the shadows, even if the green colour, copper acetate ("acetato di rame"), which Leonardo used to glaze the whole picture, has grown stronger (owing to light) altering the connections of the underlying colours and giving a certain general obscurity to the whole picture.

Also the dark coat which overlays the "Cena" may originally have been copper acetate ("acetato di rame") - see quotations from Leonardo - and it has been obviously imitated by restorers with their own colours. Dirt has later accentuated this tonality, and made it homogeneous.

From these facts one must admit that it is really difficult today to recognize and separate the overlaid colours from the original colours.

To support my thesis on Leonardo's procedure in painting his "Cena" (first priming coat of light mineral colours and subsequent darker glazings of organic colours), I quote from Leonardo's "Trattato della pittura", chapter "Del far vivi e belli i colori nelle tue pitture":

"... Sempre a quei colori che tu vuoi che abbiano bellezza, preparerai prima il campo candidissimo, e questo dico di colori che sono trasparenti perché a quelli che non sono trasparenti non giova campo chiaro... Quando un colore trasparente è sopra un altro colore variato da quello, si compone un colore misto diverso".

And the chapter "Aumentazione di bellezza nel verderame":

"...E se tu avessi finito un'opera con esso verde (verderame) semplice e poi lo velassi sottilmente con esso aloe disciolto...allora essa opera si farebbe di bellissimo colore...".

Then, to confirm that Leonardo was not a "chiarista", I quote other words of his:

"...Questo dico per quei pittori che amano tanto la bellezza del colori che senza gran coscienza danno lor debolissime e quasi insensibili ombre non stimando il lor rilievo, ed in questo errore sono i belli parlatori senza alcuna sentenza".

Now' it is evident that if one disregards the comparative research with Leonardo's best preserved works and if one disregards Leonardo's theoretic statements, it is easy not to discern the true from the false in the "Cena". Then, only if one ignores the technical procedures of the great artists of the past and the pupils' rules in their studios, it is possible to maintain that "what is under" is surely by the Master's hand.

The present restorer is removing from the "Cena" all that was added to the first mineral colour, and some superintendents enthusiastically announce that "the true Leonardo is coming to light".

But the painter who is coming to light is a "chiarista". The most probable thing is that the restorer is bringing to light that priming coat (or "campo") of light mineral colours which Leonardo described in his treatise.

And this first part of the masterpiece could also have been made with the help of pupils, as was the custom of the time.

At any rate this restoration cannot be considered a triumph.

It is an anti-historical operation and a hazard one has to look on with criticism and witness sorrowfully. Above all thinking that, in the future, perhaps, science might offer more perfect means to separate the impalpable organic colours overlaid by restorers from those overlaid by Leonardo.

The second problem concerns the preservation of what will remain of the picture after today's "cleaning".

What kind of stuff will be used to fix the coloured film to the wall?

Restorers, superintendents, the "Istituto centrale del restauro" of Rome, do not answer this question. They are all waiting for technicians to discover a suitable "fixative".

Superintendent Bertelli has declared that: "After having excluded the largely used paraloid the technicians of the "Istituto centrale" of Rome are now searching for the right fixative". In tke meantime the restorer - who is not using fixatives - hopes that: "Somebody will discover the right material" (Sunday Times and Arte).

These declarations are worrying, iust like those of the director of the "Istituto centrale" who declared they did not know the causes of the deterioration of the masterpiece.

Such declarations of impotence - at any rate - make the reasons of the presente restoration quite incomprehensible.

In July 1980 this restoration was denounced by me as inadeguate to the competent Italian Minister: it lacked a scientific diagnosis of the causes of the deterioration and a list of the materials they would use and tbe reasons for their choice.

A restoration of suck a masterpiece as Leonardo's "Cena" ought to have been decided only after verifying the causes of the deterioration, only after experimentally preparing all the suitable technical means, only after testing the compatibility of the materials to use on an autographic sample.

Objective elements lead us to the conclusion that the first draft of Leonardo's

"Cena" was executed by means of a tempera with casein glue, and the morphology of the stroke of the brush reveals an execution with mineral colours on a background kept artificially moist.

The present operation of cleaning bears an incalculable risk for its mechanical stability too.

The efficient cause of the deterioration of the picture is the wrong dosage of glue (due to Leonardo himself) in the materials for the preparation of the background in comparison with that of the coloured film. Consequently the background of preparation was softer than the coloured film, while it should have been the contrary.

To repair the first immediate damages, Leonardo retouched the picture with other organic colours (which he used without glue not to increase the tension of the film of mineral colours). Then he fixed these last glazings with a substance which, to be so glossy as Vasari notes, must have been mixed with oil.

Later, when the oil polymerized, the coloured film hardened.

In the centuries, when other restorations took place, other fixatives were used in order to arrest the falling off of colours from the wall. They made the mechanical stability of the whole picture worse and worse.

The more the coloured film hardens, the more it comes off from the ground coating of the wall. One must also remember that, in the long run, the dampness of the wall had made worse the difference between the tenacity of the background (more absorbent) and the tenacity of the coloured film.

In 1947 at last Mauro Pelliccioli, using (in a solution of alcohol) a precious animal resin, the shellac (gomma-lacca), saturated that background of preparation which is in close contact with the coloured film. So he succeeded in hardening it so as to reduce - in the end - that difference between its tenacity and the tenacity of the coloured film.

Everybody may appreciate the extraordinary quality of this restoration by looking at the picture through a stereoscopic microscope.

A crown of shellac surrounds every "clod" of colour and keeps it fixed to the bottom.

Restorer Pelliccioli forbore from removing all superimpositions of colour so as not to use the method of a solvent, which is very dangerous for the autograpbic part of a painting.

He worked only with a "bistoury" on the false parts of evident consistence.

One must remember that this restorer, besides knowing the methods and procedures of the greatest artists of the past, was himsell a very good painter and engraver.

He knew with precision where to stop his band. And, as an artist, he knew that the work of "glazing" with organic colours was the most important and masterly in the greatest masterpieces.

The solvent by means of which they are now removing varnishes, colours, retouchings, dirt from the "Cena", is considerably reducing also the consistence of the thickness of the crown of resin around the clods.

This fact will make another operation necessary in order to fix these particles of colour, with subsequent, inevitable absorption of the fixative by the coloured film; then its subsequent hardening and inevitable further peeling of the picture off the wall, especially were it fixed by means of synthetic varnish.

At any rate, today, also the use of the shellac - even if they were of opinion of using it - would be very dangeorus.

The synthetic resins moreover (though they are much recommended by superintendents) present the risk of sure damage caused by their specific nature, besides the risk of mechanical character of the shellac.

Today it is possible for everybody to verify that all old masterpieces revarnished with synthetic resins present damages of a new kind such as a loss of vividness and clearness of colour, glazed opacity etc... The planks themselves suffer new torsions as the hardness of these new resins causes tensions on the surface.

Then synthetic resins cannot be modified from case to case, nor from time to time, according to the particular requirements of each work of art. They cannot undergo variations in their degree of hardness, opacity, elasticity, velocity in the volatility of the solvents, because they are prepared according to standards.

The endurance of their characteristics is limited to a short time, while that of the natural resins is guaranteed by age-long experience.

Synthetic resins, moreover, are subiect to an early pulverization, especially under the action of ultraviolet rays and of the visible light.

In conclusion, the use of today's synthetic materials for the restoration of works of art executed in natural materials, is an unjustified and unjustifiable violence, the negative result of which can no longer be ignored by the responsible curators.

As for Leonardo's "Cena", the preservation of what remains of the painting is now tightly bound to the choice they will make as to the fixative.

This fact induces me to publish the result of a study of mine about a fixative which, through its performances, I presume will solve the problem of the peeling off of colour from the "Cena".

Fixative n. 20 - "Cena". Temperas on wall. Frescos.

The n. 20 fixative - though it has passed all laboratory proofs - should be experimented on a small portion - secondary and of few centimeters - of the "Cena".

This test on the original is necessary to draft an exhaustive and detailed report on the methodology of application with regard to its chemical and physical properties. Laboratory tests, even if carried out with the greatest accuracy, can never make use of a specimen exactly like the work of art on which one has to operate.

Therefore, a proposal for the use of this product for the "Cena" can be put forward only after a test on the original.

For the present I point out some of the properties of this fixative and suggest a test (on few centimeters of the picture in a marginal zone) to the responsible Curators.

The preparation is highly hygrorepulsive. It does not polymerize, therefore it does not crush or crumble. It does not cause tensions on the surface. It does not contain oils. Time and light improve its already sufficiently high qualities of transparency.

It is not glossy, and so it makes the legibility of the picture perfect.

Its hardness, when the solvent is volatilized, is between 2 and 3 of the Mohs scale, that is the best with regard to the hardness of the chalk and that of the coloured film, which is very hard. (This preparation can be brought to hardness between 3 and 4, according to necessity, without causing, nevertheless, tensions on the surface).

No other fixative possesses such physical characteristics, which are essential in fixing the clods of colour.

The classic fixatives on the market are all very hard. Some resins, natural as well artificial reach hardness 6.

Should restorers use such substances for the "Cena", the picture would be destroyed because of a rapid scraping. The fixative I am proposing is easily removable, both by means of solvents (being reversible), and mechanically.

Light - as alreaday said - improves the transparency of its substances more and more, thus improving its high colourless quality.